Here is a detailed step by step procedure of how you can reset / refresh your Windows 8 PC and also reset the Trial period.
Step 1: Simply launch Metro >> Control Panel or PC settings. You can easily do this by simultaneously pressing Windows + I keys followed by Enter key.
Step 2: In the left pane, click on General option to see Reset your PC and Refresh your PC options. Click on Get Started button under Reset your PC or Refresh your PC. With this option you will not be asked to insert the installation or recovery media message this time around.
Hope this step-by-step procedure to Reset Windows 8 PC helped you overcome the trial period.